class Solution {
public:
    long long countCompleteDayPairs(vector<int>& hours) {
        long long ret = 0;
        vector<int> node(24);
        for(auto &e: hours){
            ret +=node[(24 - e%24)%24];
            node[e%24]++;
        }
        // for(auto &e :node){
        //     cout << e<<' ';
        // }
        return ret;
    }
};